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Re: [css3-3d-transforms] matrix3d() uses column-major order, but CSSMatric properties row-major ?

From: Brendan Kenny <bckenny@gmail.com>
Date: Thu, 9 Sep 2010 15:25:01 -0500
Message-ID: <AANLkTim=WJd9jROb0fuSJGck+uR8Yiq+uXhec=pRFbop@mail.gmail.com>
To: Chris Marrin <cmarrin@apple.com>
Cc: Boris Zbarsky <bzbarsky@mit.edu>, "www-style@w3.org list" <www-style@w3.org>
On Thu, Sep 9, 2010 at 1:08 PM, Chris Marrin <cmarrin@apple.com> wrote:
>
> On Sep 9, 2010, at 9:26 AM, Boris Zbarsky wrote:
>
>>> Yes I agree that this can be more clear. But to be clear a proper homogeneous multiplication of a matrix by a vector would divide the resultant x, y, z values by the 4th component, w.
>>
>> Sure (unless w == 0, etc).  But the point is, the spec needs to define all this, either inline or by reference.
>
> Right. The only way w could equal 0 is if the matrix is singular, You'd have to catch this case, but rendering would not be an issue.
>
> -----
> ~Chris
> cmarrin@apple.com

Is the intent for perspective to be added only via the perspective
property, then? Because (some) perspective transforms are nonsingular
and map all the points in the eye plane (for instance) to the plane at
infinity.

I actually agree with both of you; these problems are all well known
and unsurprising, but there are some ambiguities that would be cleared
up (or at least some detective work avoided) with more explicit
transformation definitions (a la the SVG coordinate
system/transformation section[1]).

[1] http://www.w3.org/TR/SVG/coords.html#TransformMatrixDefined
Received on Thursday, 9 September 2010 20:25:35 GMT

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